U.S. patent number 7,228,191 [Application Number 10/429,288] was granted by the patent office on 2007-06-05 for method and apparatus for constructing crowns, bridges and implants for dental use.
This patent grant is currently assigned to Geodigm Corporation. Invention is credited to Andrew Hofmeister, Bruce Hultgren, Bob Isaacson, James Ledin, Mike Marshall.
United States Patent |
7,228,191 |
Hofmeister , et al. |
June 5, 2007 |
**Please see images for:
( Certificate of Correction ) ** |
Method and apparatus for constructing crowns, bridges and implants
for dental use
Abstract
A method, apparatus, and article of manufacture is disclosed for
providing a dental crowns using electronic models, and more
particularly to a method, apparatus, and article of manufacture for
creating dental crowns using a lost-wax manufacturing process from
electronic model files corresponding to patient teeth impressions
and corresponding electronic models for tooth crowns. The system
and method permit the electronic generation and specification of
crown, bridge, and implant dental appliances that may be specified
in an industry standard file specification. This specification is
utilized in a rapid prototyping process to generate a wax
impression for the appliance that may then be fabricated using
standard lost-wax fabrication techniques.
Inventors: |
Hofmeister; Andrew (Chanhassen,
MN), Ledin; James (Chanhassen, MN), Isaacson; Bob
(Edina, MN), Hultgren; Bruce (Victoria, MN), Marshall;
Mike (Savage, MN) |
Assignee: |
Geodigm Corporation
(Chanhassen, MN)
|
Family
ID: |
33310576 |
Appl.
No.: |
10/429,288 |
Filed: |
May 2, 2003 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20040220691 A1 |
Nov 4, 2004 |
|
Current U.S.
Class: |
700/98; 700/117;
433/223; 700/119; 433/218 |
Current CPC
Class: |
A61C
13/0004 (20130101); B33Y 50/00 (20141201); B33Y
80/00 (20141201); A61C 5/77 (20170201); A61C
13/20 (20130101) |
Current International
Class: |
G06F
19/00 (20060101); A61C 5/10 (20060101) |
Field of
Search: |
;700/98,182,117,118,119,120 ;433/6,24,213,29,183 ;382/154 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 316 106 |
|
May 1989 |
|
EP |
|
0 502 227 |
|
Nov 1996 |
|
EP |
|
2 593 384 |
|
Jan 1986 |
|
FR |
|
5049651 |
|
Mar 1993 |
|
JP |
|
WO 94/10935 |
|
May 1994 |
|
WO |
|
WO 02/19940 |
|
Mar 2002 |
|
WO |
|
WO 02/076327 |
|
Oct 2002 |
|
WO |
|
Other References
Lewis, J., "Software beefs up tractor radiator-guard mount," Design
News, vol. 54, No. 4, pp. 87-88 (Feb. 15, 1999) (1 page abstract).
cited by other .
Rotert, V., "How one rapid prototyping method is able to eliminate
tooling for investment casting," Proceedings of the 45th Annual
Technical Meeting and Exhibition Investment Casting Institute,
Atlanta, Georgia (1997) (1 page abstract). cited by other .
Weeden, B. et al., "Alternate methods for custom implant production
utilizing a combination of rapid prototyping technology and
conventional investment casting," Proceedings of the 1996 15th
Southern Biomedical Engineering Conference, Dayton, Ohio (1996) (1
page abstract). cited by other .
Wirtz, H. et al., "Investment casting shells in 1 day using
selective laser sintering (SLS)," Proceedings of the 24th BICTA
Conference on Investment Casting, Oxford, GB (1999) (1 page
abstract). cited by other .
Wu, M. et al., "Application of rapid prototyping and numerical
simulation in titanium dental castings," Computer Assisted Surgery
& Rapid Prototyping in Medicine, 5th Int. Workshop (1999) (1
page abstract). cited by other.
|
Primary Examiner: Picard; Leo
Assistant Examiner: Kasenge; Charles
Attorney, Agent or Firm: Merchant & Gould P.C.
Claims
What is claimed is:
1. A method for constructing a dental appliance for a patient,
comprising: displaying an electronic model of at least a portion of
the teeth of the patient, the displayed portion including a prep
site; generating a definition for a margin curve around the prep
site; refining the margin curve; creating an electronic model of
the dental appliance to be installed on the prep site including;
selecting a first mesh surface from a library of mush surfaces;
generating a second mesh surface defined by the refined margin
curve; and generating a third mesh surface extending between a
perimeter of the first mesh surface and the margin curve of the
second mesh surface; creating an electronic specification from the
electronic model; and generating a model from the electronic
specification using rapid prototyping.
2. The method of claim 1, further comprising fabricating a dental
appliance from the wax model using a lost wax process.
3. The method of claim 1, wherein generating the second mesh
surface includes generating the second mesh surface with allowance
for an offset space between the prep site and the second mesh
surface.
4. The method of claim 1, further comprising displaying the
electronic model of the dental appliance on the prep site of the
displayed portion of the teeth of the patient.
5. The method of claim 1, further comprising: defining a set of
scaling match points on the margin curve; scaling the first mesh
surface to a proper size using the set of scaling match points.
6. The method of claim 1, further comprising: placing an image of
at least one mesh surface on the prep site; enabling manipulation
of the position and orientation of at least one of the first and
third mesh surfaces relative to the prep site to place the mesh
surface into a desired position.
7. The method of claim 1, wherein the dental appliance to be
created is a crown, a bridge or an implant.
8. The method of claim 1, wherein the displayed portion of the
teeth of the patient includes the prep site and at least one tooth
adjacent to the prep site.
9. The method of claim 2, wherein the fabricated dental appliance
substantially corresponds to the electronic model of the dental
appliance.
10. The method of claim 7, wherein the dental appliance to be
created is a crown, and the electronic model of the crown is
created using a crown top mesh, a crown side mesh, and a crown
offset prep mesh.
11. The method of claim 6, further comprising: scaling the first
mesh surface to a proper size; and scaling the third mesh surface
to create adequate separation between the dental appliance and/at
least one adjacent tooth.
12. The method of claim 6, further comprising scaling the second
mesh surface to permit an adhesive to be placed between the prep
site and the dental appliance.
13. The method of claim 6, further comprising modifying the shape
of the second mesh to eliminate at least one undercut shape in its
surface.
14. A processing system for creating at least one dental appliance
to be installed onto a prep site, comprising: a model manipulation
module that allows a user to view, position, scale, and size at
least one model polygonal mesh on a computer display; a margin
curve processing module that generates a refined margin curve; a
model polygonal mesh generation module configured to generate a
polygonal mesh defined by the refined margin curve; a model
polygonal mesh specification module that generates an output file
comprising a specification for a dental appliance, the
specification configured for use in a rapid prototyping process;
and a library of surfaces that represent occlusal surfaces of teeth
known to be within the human mouth.
15. The processing system of claim 14, wherein the library includes
electronic polygonal mesh representations of various dental
appliances.
16. The processing system of claim 14, wherein the margin curve
processing module includes: a define module for defining a margin
curve around a prep site; a cab refine margin point module that
generates a refined margin point; and a generate reined point curve
module; wherein the generate reined point curve module generates a
modified mesh surface that moves the margin curve to the refined
margin point for all points along the margin curve; wherein the
refined margin points define the refined margin curve.
17. The processing system of claim 14, wherein the model mesh
generation module includes; a top mesh module that generates or
enables selection from the library of a top mesh surface; an offset
mesh module that generates an offset mesh surface based on the
refined margin curve; a side mesh module that generates a side mesh
surface extending between the refined margin curve and a perimeter
of the top mesh surface; and a combine mesh module that combines
the top mesh, the side mesh, and the offset mesh together to define
the final volume for the dental appliance.
18. A method for constructing a dental appliance for a patient,
comprising: displaying an electronic model of at least a portion of
the teeth of the patient, the displayed portion including a prep
site that requires the dental appliance; and generating a
definition for a margin curve around the prep site; refining the
margin curve; creating an electronic model of the dental appliance
to be installed on the prep site, wherein the electronic model of
the dental appliance is crested using at least a first, second, and
third polygonal mesh that represent different surfaces of the
dental appliance to be formed, and wherein the refined margin curve
defines the boundaries of one of the polygonal meshes, and wherein
creating the electronic model of the dental appliance includes:
selecting a first mesh surface from a library of mesh surfaces;
generating a second mesh surface defined by the margin curve with
allowance for an offset space between the prep site and the second
mesh surface; and generating a third mesh surface extending between
a perimeter of the first mesh surface and the margin curve of the
second mesh surface; creating an electronic specification from the
electronic model; and generating a wax model from the electronic
specification using rapid prototyping.
Description
TECHNICAL FIELD
This application relates in general to a method, apparatus, and
article of manufacture for providing a dental crowns using
electronic models, and more particularly to a method, apparatus,
and article of manufacture for creating dental crowns using a
lost-wax manufacturing process from electronic model files
corresponding to patient teeth impressions and corresponding
electronic models for tooth crowns.
BACKGROUND OF THE INVENTION
Recently, computing systems have increased in computational power
to permit the development of processing systems to generate,
manipulate and utilize electronic mesh-based models for physical
objects having sufficient spatial resolution to permit the
replacement of physical models in many applications. The dental
industry has for a long time utilized physical models to observe
the interaction of patient's teeth with opposing teeth as well as
the introduction of dental appliances such as crowns, bridges and
implants (CBI) into a patient's mouth. These models are utilized to
select, size and orient the CBI devices before the devices are
placed into a patient's mouth. This use of physical models is
expensive as it requires the creation of multiple models as a
patient's treatment plan progresses. In addition, these physical
models must be stored for later retrieval.
Computer based systems that allow the creation and use of
electronic models of these impressions of teeth have been developed
over time. Examples of such systems are described in U.S.
Provisional Patent Application entitled, "METHOD AND APPARATUS FOR
COMPUTER GENERATION OF ELECTRONIC MODEL IMAGES", Ser. No.
60/351,270 filed Jan. 22, 2002, now U.S. patent application
entitled, "METHOD AND APPARATUS FOR COMPUTER GENERATION OF
ELECTRONIC MODEL IMAGES", Ser. No. 10/350,302, filed Jan. 22, 2003;
and U.S. Provisional Patent Application entitled, "METHOD AND
APPARATUS FOR AUTOMATICALLY DETERMINING THE LOCATION OF INDIVIDUAL
TEETH WITHIN ELECTRONIC MODEL IMAGES", Ser. No. 60/351,271, filed
Jan. 22, 2002, now U.S. patent application entitled, "METHOD AND
APPARATUS FOR AUTOMATICALLY DETERMINING THE LOCATION OF INDIVIDUAL
TEETH WITHIN ELECTRONIC MODEL IMAGES", Ser. No. 10/350,304, filed
Jan. 22, 2003. These applications are commonly assigned with the
instant application and are incorporated by reference herein. These
prior systems generated the electronic models and systems used to
permit dentists to use the models in place of the physical models.
The prior systems permit the manipulation of teeth within the model
are part of designing a treatment plan for a patient.
These earlier systems, however, do not utilize dental CBI
appliances in the electronic model processing. If an electronic
model for such a CBI appliance is constructed electronically to fit
a prep site found in an electronic model for a patient, a custom
CBI appliance may be constructed that more accurately matches the
patient's mouth. The entire manipulation of the CBI appliance may
be performed electronically to obtain a more optimum dental
solution for a patient with a resulting CBI appliance device
created using a standard lost-wax manufacturing process based upon
an electronic model generated for the CBI appliance. The present
invention addresses the above limitations of prior dental
electronic modeling systems.
SUMMARY OF THE INVENTION
In accordance with the present invention, the above and other
problems are solved by providing a method, apparatus, and article
of manufacture for providing a dental crowns using electronic
models, and more particularly to a method, apparatus, and article
of manufacture for creating dental crowns using a lost-wax
manufacturing process from electronic model files corresponding to
patient teeth impressions and corresponding electronic models for
tooth crowns.
The great utility of the invention is that the system and method
permit the electronic generation and specification of crown,
bridge, and implant dental appliances that may be specified in an
industry standard file specification. This specification is
utilized in a rapid prototyping process to generate a wax
impression for the appliance that may then be fabricated using
standard lost-wax fabrication techniques.
These and various other features as well as advantages, which
characterize the present invention, will be apparent from a reading
of the following detailed description and a review of the
associated drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings in which like reference numbers
represent corresponding parts throughout:
FIG. 1 illustrates an example of an electronic model for a dental
crown constructed according to one embodiment of the present
invention.
FIG. 2 illustrates a side view of an electronic model of a dental
impression of a patient's teeth used in creation of a dental crown
constructed according to one embodiment of the present
invention.
FIG. 3 illustrates a general purpose computing system for use in
implementing as one or more computing embodiments of the present
invention.
FIGS. 4a 4c illustrate various views of a tooth prep site used to
construct a dental crown according to one embodiment of the present
invention.
FIG. 5 illustrates a cross-section view of a crown, its
corresponding prep site and adjacent teeth in preparation for
construction of a dental crown in accordance with an embodiment of
the present invention.
FIGS. 6a 6b illustrate creation of a refined margin curve point
used in construction of a dental crown in accordance with another
embodiment of the present invention.
FIGS. 7a 7d illustrate various views of an electronic model for a
dental crown constructed according to an embodiment of the present
invention.
FIG. 8 illustrates identification of match points on an electronic
model of dental impressions of teeth used to size a crown device
according to an example embodiment of the present invention.
FIGS. 9a 9b illustrate placement of a dental crown upon a prep site
using previously selected match points according to an embodiment
of the present invention.
FIGS. 10a 10c illustrate correcting placement and orientation of a
dental crown upon a prep site using previously selected match
points according to an embodiment of the present invention.
FIGS. 11a 11b illustrates electronic construction of side meshes
between a properly oriented crown and a margin curve of a prep site
according to an embodiment of the present invention.
FIGS. 12a 12b illustrate electronic construction of side meshes
having various curved shapes between a properly oriented crown and
a margin curve of a prep site according to an embodiment of the
present invention.
FIG. 13 illustrates a set of processing modules within a CBI
processing system utilizes to implement a method for creating
dental crowns using a lost-wax manufacturing process from
electronic model files corresponding to patient teeth impressions
and corresponding electronic models for tooth crowns.
FIG. 14 illustrates an operational flow for a method for creating
dental crowns using a lost-wax manufacturing process from
electronic model files corresponding to patient teeth impressions
and corresponding electronic models for tooth crowns.
DETAILED DESCRIPTION
This application relates in general to a method, apparatus, and
article of manufacture for creating dental crowns using a lost-wax
manufacturing process from electronic model files corresponding to
patient teeth impressions and corresponding electronic models for
tooth crowns, bridges and implant devices.
FIG. 1 illustrates an example of an electronic model for a dental
crown constructed according to one embodiment of the present
invention. In this example embodiment, a completed electronic model
100 for a crown is shown in the position it is to be installed
within a patient's mouth as it is positioned within an electronic
model for an impression of a patient's lower teeth. The electronic
model for a patient's teeth corresponds to a polygonal mesh created
from an electronic scan of a dental impression of a patient's
mouth. An example of a system that generates such an electronic
model is described within U.S. Provisional Patent Application
entitled, "METHOD AND APPARATUS FOR COMPUTER GENERATION OF
ELECTRONIC MODEL IMAGES", Ser. No. 60/351,270 filed Jan. 22, 2002,
now U.S. patent application entitled, "METHOD AND APPARATUS FOR
COMPUTER GENERATION OF ELECTRONIC MODEL IMAGES", Ser. No.
10/350,302, filed Jan. 22, 2003; and U.S. Provisional Patent
Application entitled, "METHOD AND APPARATUS FOR AUTOMATICALLY
DETERMINING THE LOCATION OF INDIVIDUAL TEETH WITHIN ELECTRONIC
MODEL IMAGES", Ser. No. 60/351,271, filed Jan. 22, 2002, now U.S.
patent application entitled, "METHOD AND APPARATUS FOR
AUTOMATICALLY DETERMINING THE LOCATION OF INDIVIDUAL TEETH WITHIN
ELECTRONIC MODEL IMAGES", Ser. No. 10/350,304, filed Jan. 22,
2003.
The output from the scanning process includes the generation of an
electronic model representing the physical representation of the
scanned study cost. The electronic model consisting of a polygonal
mesh used to represent the seen face of the study cast. Such an
electronic model may be created using a process described in
commonly assigned U.S. Provisional Patent Application, "Method and
Apparatus for Computer Generation of Electronic Model Images" Ser.
No. 60/351,270, filed Jan. 27, 2002, now U.S. patent application,
"Method and Apparatus for Computer Generation of Electronic Model
Images" Ser. No. 10/305,302, filed Jan. 22, 2003.
Additionally, the electronic models may also be created using a CT
Scan of an impression, rather than scanning the study cast, using
commercially available CT scanning processes such as a process
developed by Hytec Corp. of Los Alomos, N. Mex. This process also
generates an electronic model consisting of a polygonal mesh. In
both cases, the generated polygonal mesh is used in subsequent
processing independent of the source of the electronic model.
An operator of a computing system generates an electronic model for
the crown appliance as described herein to obtain a custom designed
appliance that matches the available space in the patient's mouth.
Once the electronic model for the crown appliance is completed to
the satisfaction of the dental professional, the crown appliance
may be manufactured using any manufacturing processing that accepts
electronic models for physical objects expressed in a standard
form. In a preferred embodiment, the manufacturing process utilizes
a lost-wax manufacturing process in which the electronic model of
the crown device is specified in a standard STL specification file.
The STL specification file is used to generate a wax impression for
the crown appliance using any type of rapid prototyping process
that is well known in the prototyping industry. One skilled in the
art will recognize that any type rapid prototyping processes may be
used without deviating from the spirit and scope of the present
invention as recited within the attached claims. In addition,
throughout this application, an example embodiment is illustrated
using the generation of a dental crown appliance; one skilled in
the art will easily recognize that other CBI appliances may be
readily constructed in accordance with the present invention as
recited in the attached claims.
FIG. 2 illustrates a side view of an electronic model of a dental
impression of a patient's teeth used in creation of a dental crown
constructed according to one embodiment of the present invention.
In this embodiment, the dental impression model includes an upper
teeth portion 103 and a lower teeth portion 102. The lower teeth
portion 102 possesses a prep site 401 that represents the location
at which a crown appliance is to be inserted. The upper teeth
portion 103 are positioned relative to the lower teeth portion 102
to illustrate the interaction of the opposing teeth as a patient's
mouth is opened and closed. In the position shown in FIG. 2, the
teeth are positioned as they would be when the patient has his or
her mouth completely closed. As disclosed in earlier applications
of the assignee, the upper portion 103 and the lower portion 102 of
the electronic model of these teeth may be moved relative to each
other to permit the study of the interaction of opposing teeth, and
in the instant application, opposing teeth and a crown
appliance.
With reference to FIG. 3, an exemplary system for implementing the
invention includes a general-purpose computing device in the form
of a conventional personal computer 300, including a processor unit
312, a system memory 316, and a system bus 322 that couples various
system components including the system memory 316 to the processor
unit 312. The system bus 322 may be any of several types of bus
structures including a memory bus or memory controller, a
peripheral bus and a local bus using any of a variety of bus
architectures. The system memory includes read only memory (ROM)
332 and random access memory (RAM) 316. A basic input/output system
318 (BIOS), which contains basic routines that help transfer
information between elements within the personal computer 300, is
stored in ROM 318.
The personal computer 300 further includes a hard disk drive 338
for reading from and writing to a hard disk, a magnetic disk drive
for reading from or writing to a removable magnetic disk, and an
optical disk drive 326 for reading from or writing to a removable
optical disk such as a CD ROM, DVD, or other optical media. The
hard disk drive 338, magnetic disk drive, and optical disk drive
326 are connected to the system bus 322 by a hard disk drive
interface, a magnetic disk drive interface, and an optical drive
interface, respectively. The drives and their associated
computer-readable media provide nonvolatile storage of computer
readable instructions, data structures, programs, and other data
for the personal computer 300.
Although the exemplary environment described herein employs a hard
disk 338, a removable magnetic disk, and a removable optical disk
326, other types of computer-readable media capable of storing data
can be used in the exemplary system. Examples of these other types
of computer-readable mediums that can be used in the exemplary
operating environment include magnetic cassettes, flash memory
cards, digital video disks, Bernoulli cartridges, random access
memories (RAMs), and read only memories (ROMs).
A number of program modules may be stored on the hard disk 338,
magnetic disk, optical disk 326, ROM 332 or RAM 316, including an
operating system 320, one or more application programs 330, other
program modules 334, and program data 336. A user may enter
commands and information into the personal computer 300 through
input devices such as a keyboard and mouse or other pointing
device. Examples of other input devices may include a microphone,
joystick, game pad, satellite dish, and scanner. These and other
input devices are often connected to the processing unit 312
through a I/O port interface 324 that is coupled to the system bus
332. Nevertheless, these input devices also may be connected by
other interfaces, such as a parallel port, game port, or a
universal serial bus (USB). A monitor or other type of display
device is also connected to the system bus 332 via an interface,
such as a video adapter 314. In addition to the monitor, personal
computers typically include other peripheral output devices (not
shown), such as speakers and printers.
The personal computer 300 may operate in a networked environment
using logical connections to one or more remote computers, such as
a remote computer. The remote computer may be another personal
computer, a server, a router, a network PC, a peer device or other
common network node, and typically includes many or all of the
elements described above relative to the personal computer 300. The
network connections include a local area network (LAN) and a wide
area network (WAN). Such networking environments are commonplace in
offices, enterprise-wide computer networks, intranets, and the
Internet.
When used in a LAN networking environment, the personal computer
300 is connected to the local network through a network interface
or adapter 310. When used in a WAN networking environment, the
personal computer 300 typically includes a modem or other means for
establishing communications over the wide area network, such as the
Internet. The modem 254, which may be internal or external, is
connected to the system bus 332 via the I/O port interface 324. In
a networked environment, program modules depicted relative to the
personal computer 300, or portions thereof, may be stored in the
remote memory storage device. It will be appreciated that the
network connections shown are exemplary, and other means of
establishing a communications link between the computers may be
used.
Additionally, the embodiments described herein are implemented as
logical operations performed by a computer. The logical operations
of these various embodiments of the present invention are
implemented (1) as a sequence of computer implemented steps or
program modules running on a computing system and/or (2) as
interconnected machine modules or hardware logic within the
computing system. The implementation is a matter of choice
dependent on the performance requirements of the computing system
implementing the invention. Accordingly, the logical operations
making up the embodiments of the invention described herein can be
variously referred to as operations, steps, or modules.
FIGS. 4a 4c illustrate various views of a tooth prep site used to
construct a dental crown according to one embodiment of the present
invention. In these figures, a prep site 401 that represents a
location on an electronic model where a crown appliance it to be
constructed and installed. The prep site 401 is typically defined
as the portion of the patient's tooth that is to be covered by a
crown appliance. The area underneath the crown appliance is defined
to be the area within a margin curve 410 that identifies the point
in space where the patient's existing tooth meets the outer edge of
the crown appliance. When the crown appliance is installed within
the patient's mouth, the margin curve will define the transition
from the patient's teeth and jaw structure to an outer surface of
the crown. FIG. 4a illustrates the prep site 401 and the margin
curve 410 as it would be seen from the outer side of teeth. FIG. 4b
illustrates the same prep site 401 and the corresponding margin
curve 410 as it would be seen from the inner side of teeth. FIG. 4c
illustrates the prep site 401 and its margin curve 410 as it would
be seen from top view of the teeth. The margin curve 410 is shown
in FIG. 4c as completely encircling the prep site 401 as the crown
appliance will cover the entire prep site 401.
FIG. 5 illustrates a cross-section view of a crown, its
corresponding prep site and adjacent teeth in preparation for
construction of a dental crown in accordance with an embodiment of
the present invention. In this embodiment, a crown appliance 500
constructed from a crown top 501, a crown side 502, and a crown
offset prep 503 polygonal mesh is placed upon a prep site 401. The
crown appliance 500 is shown relative to its adjacent teeth 510,
511. The crown top 501 corresponds to the top portion of a crown
that corresponds to the occlusal surface that interacts with an
opposing tooth. Typically, the crown top 501 is selected from a
library of crown shapes that are stored within a computer-based
dental modeling system. This library of teeth are pre-constructed
shapes that represent the various teeth known to be within a human
mouth. The dental professional selects the crown top 501 from the
library that corresponds to the type of tooth to be created by the
crown appliance.
In a preferred embodiment, this library of crown tops comprise
electronic polygonal mesh representation of standard crown shapes
that have been scanned using a process similar to the one used to
generate the electronic model of the patient's teeth 102, 103. For
example, the University of Minnesota School of Dentistry is known
to possess a standard set of crown top shapes that have been
modeled by Professor Fred Nobel to provide representative tooth
shapes. These shapes have been sculpted to both provide useful
opposing tooth surfaces needed by a patient in chewing food and
provide aesthetically pleasing teeth in a patient's mouth. Of
course, any such library of crown top shapes may be utilized with
the present invention without deviating from the spirit and scope
of the present invention as recited within the attached claims.
Alternatively, electronic models of crown tops, such as ones
commercially available from Productivity Training Corporation, of
Morgan Hill Calif., may also be used without deviating from the
spirit and scope of the present invention as recited in the
attached claims.
The crown side 502 corresponds to the polygonal mesh created to
mate the crown top 501 to the margin curve 410 along the outer edge
of the crown appliance 500. Once a crown top 501 is selected, sized
properly, and placed into its proper position, the crown side 502
may be constructed to define this outer shape of the crown
appliance 500. The shape of the crown side 502 may be checked for
its position relative to the adjacent teeth 510, 511 for regions of
space where the surfaces may co-exist. The shape of the crown side
502 may be modified as needed to create adequate separation from
the crown appliance 500 and the adjacent teeth 510, 511.
The crown offset prep 503 polygonal mesh corresponds to the inner
surface of the crown appliance 500 and is shaped to correspond to
the contours of the prep site 401 within the margin curve 410. The
crown offset prep 503 mesh is defined to provide an offset space
521 between the prep site 401 and the crown offset prep 503 mesh
that is sufficient to permit an adhesive to be placed between the
prep site surface 401 and the crown appliance 500 that will hold
the crown appliance 500 in place. The area between the crown top
501, crown side 502, and the crown offset prep 503 mesh represents
the region of space to be filled by the crown appliance material,
such as gold or ceramic dental material.
The crown prep mesh 503 is also checked to ensure that the crown
appliance may be placed onto the prep site 401 along a path of an
insertion vector 530. The completed crown appliance is typically
installed following a straight vector path of travel. As a result,
the inner shape of the offset prep mesh 503 is checked to identify
and eliminate any undercut shapes in its surface that would prevent
the insertion of the crown appliance onto the prep site. Typically,
additional space is left in the offset space 521 for this undercut
volume that may be filled by additional adhesive.
The processing system generates an electronic specification for the
combination of these three polygonal meshes, the crown top 501,
crown side 502, and the crown offset prep 503 meshes. This
electronic specification is used to generate the rapid prototyping
wax that may be used in a conventional lost wax manufacturing
technique to create the crown appliance 500.
FIGS. 6a 6b illustrate creation of a refined margin curve point
used in construction of a dental crown in accordance with another
embodiment of the present invention. In a preferred embodiment, the
margin curve 410 that is used to define the transition point
between a patient's teeth and the crown appliance 100 is moved to a
refined curve point 621 within the electronic model of the teeth
102. Typically, the margin curve point 410 appears as having a
rounded edge as shown in FIG. 6a. This rounded edge appears to be
created from the scanning and processing within the electronic
modeling system 300 and may not accurately represent the point in
space where the margin curve should exist.
As a result, the refined margin curve 621 is defined by projecting
a line tangent to the horizontal 602 and vertical 603 surfaces from
the prep site 401 on either side of the margin curve 410. The point
of intersection for these two projected tangent lines 602, 603 is
defined as the refined margin curve point for any given point on
the margin curve. The prep site 401 surface of the polygonal mesh
is modified to move the margin curve point 410, and its
corresponding adjacent surface to the refined margin curve point
621 as shown in FIG. 6b. This process is shown for a single point
on the margin curve surface 410 and is repeated for all points
along the margin curve surface 410. The revised margin curve 621 is
used in all subsequent processing to generate the crown appliance
500.
FIGS. 7a 7d illustrate various views of an electronic model for a
dental crown constructed according to an embodiment of the present
invention. FIGS. 7a and 7b illustrate the crown appliance 100 shown
from the crown top perspective. FIGS. 7c and 7d illustrate the
crown appliance 101 from the crown offset prep mesh perspective.
When one compares the surface of the offset prep mesh shown in
FIGS. 7c and 7d, the surfaces match the prep site surfaces shown in
detail in FIGS. 4a 4c. The shape of the bottom edge of the crown
appliance 100 also matches the margin curve 410 discussed above
with respect to FIGS. 4a 4c.
FIG. 8 illustrates identification of match points on an electronic
model of dental impressions of teeth used to size a crown device
according to an example embodiment of the present invention. In
order to create the crown appliance 100 shown above in FIGS. 7a 7d,
a crown top is selected from the library of electronic models for
the crown tops. These library models are sized to a normalized size
and are adjusted to fit the individual patient. The crown top is
sized to fit the prep site 401 by an operator selecting at least
two points 810 811 along a line 801 across one dimension of the
prep site 410. Typically, the line 801 is selected such that end
points 810 811 correspond to the widestpoints across the particular
dimension of the prep site 401. These points also lie on the margin
curve 410.
Once these two points are selected, the length of the line 801 is
determined for use in properly sizing the crown top. The normalized
crown top is scaled in size to correspond to the length of the
identified line 801. The crown top is scaled in all dimensions to
preserve the relationships and aspect ration for the crown top. If
more than two points are selected, the crown top may be scaled in
additional dimensions to fit the prep site 401. Typically, only one
line is selected as it permits the crown top to scale in a manner
that preserves the occlusal shape of the crown top.
FIGS. 9a 9b illustrate placement of a dental crown upon a prep site
using previously selected match points according to an embodiment
of the present invention. The scaled crown top 901 is placed upon
the prep site in the position in which it is expected to reside
once installed. The computing system superimposes the electronic
model of the crown top 901 upon the electronic model of the jaw 102
containing the prep site 401. The placement of the crown top 901
may be viewed from a top view as shown in FIG. 9a and a side view
as shown in FIG. 9b. The margin curve 410 is shown in these views
to identify the prep site and allow proper placement of the crown
top 901.
The operator may move and position the crown top 901 into position
that corresponds to a desired location once the crown appliance is
completed. This manual process of placing and orienting the crown
top continues until the position satisfies the dental
professional.
FIGS. 10a 10c illustrate correcting placement and orientation of a
dental crown upon a prep site using previously selected match
points according to an embodiment of the present invention. The
crown top 901 must also be oriented to place the top surface of the
crown top in a position to properly engage the opposing tooth. FIG.
10a illustrates the shifting of the orientation of the crown top
901 to a desired position that appears to more accurately track the
orientation of the margin curve. FIG. 10b illustrates positioning
the upper teeth model 103 into their position to verify that the
crown top 901 properly interacts with the opposing tooth. The
operator may again modify the position and orientation of the crown
appliance 901 to allow points of contact 1001 between the crown top
901 and the opposing teeth 103 to be properly positioned as is FIG.
10c.
Because the computing system permits the electronic models to be
rotated and moved in any direction, the operator may verify the
position and interaction 1002 of the crown top 901 with the other
teeth of the patient until satisfied that the crown top 901 is
position in the optimum position. Once positioned, the computing
system may define the side mesh and the offset prep mesh between
the crown top and the margin curve 410 as discussed above.
FIGS. 11a 11b illustrates electronic construction of side meshes
between a properly oriented crown and a margin curve of a prep site
according to an embodiment of the present invention. The side mesh
is constructed to create a smooth surface between the edge 1101 of
the crown top 901 and the margin curve 410. Any smooth shape, that
typically possesses a modest curve, may be used to create a crown
appliance that is both functional and aesthetically pleasing. The
operator defines these two curves 1101 and 410 and the computer
system automatically generates a side mesh as shown in FIG. 11b.
The side mesh is also created to avoid interaction with the
adjacent teeth. The operator modifies the side mesh as necessary to
obtain the desired shape.
The offset prep mesh is also automatically created to provide at
least a minimum offset space between the offset prep mesh and the
prep site 401. The three meshes, the crown top mesh, the side mesh
and the offset prep mesh are combined together to define the final
volume for the crown appliance.
FIGS. 12a 12b illustrate electronic construction of side meshes
having various curved shapes between a properly oriented crown and
a margin curve of a prep site according to an embodiment of the
present invention. FIG. 12a illustrates the shape of the side mesh
being varied to obtain a desired shape and avoid the interaction of
the side of the crown appliance with adjacent teeth. In this
example, a crown top 1201 is shown above a margin curve 1202. A
side mesh 1211 is shown connecting the two surfaces. The operator
may modify the shape of the side mesh by moving the surface 1212 to
a desired position. Any type of graphical manipulation of the side
surface may be used as part of the shaping of the sides of the
crown.
In a preferred embodiment, a user specifies one or more parameters
that are used to specify the rate of change for the slope of the
side surface. The side surface 1212 is defined by a plane tangent
1221 to the crown top 1201 at the point where the two surfaces
interface. Similarly, the side surface is defined by a plane
tangent 1222 at the margin line 1202. The side surface 1212 is
defined as a series of polygonal surfaces along a path between
these two planes where the slope of the surface is varied from the
slope of the first tangent plane 1221 and the second tangent plane
1222. The side surfaces are typically varied to allow the side
surface to contact adjacent teeth to prevent movement of the tooth
while still providing sufficient spacing to permit the insertion of
the crown onto the prep site. The user may vary the parameters to
obtain a desired shape for the side surfaces. The process will
continue until the dental professional is satisfied with the shape
of the side mesh.
Once the electronic model for the crown appliance is completed, the
crown appliance may be manufactured using any manufacturing
processing that accepts electronic models for physical objects
expressed in a standard form as discussed above. In a preferred
embodiment, a standard STL specification file is utilized to define
the volume for the crown appliance that is to be manufactured. The
STL specification file is used generate a wax impression for the
crown appliance using a rapid prototyping process that is well
known in the prototyping industry. The wax impression may be used
in a lost-wax fabrication process to make the crown appliance out
of any suitable dental material such as gold or ceramic material.
Of course, one skilled in the art will recognize that any type of
rapid prototyping methods may be utilized to make such CBI products
without deviating from the spirit and scope of the present
invention as recited within the attached claims. One such
alternative rapid prototyping process is a deposition process that
prints gold and ceramic material to create dental appliances
available from Optomec Inc. of Albuquerque N. Mex. Other
alternative fabrication techniques may also include milling of
dental appliance materials and use of electrical discharge
machining techniques as are well known in the art.
In addition to creating an appliance as described above, the model
for the appliance may be manually edited or sculpted once created
to define the final definition for the appliance before it is
fabricated. This sculpting is performed electronically on the
electronic model once created as illustrated in FIG. 12c. The
surface of the electronic model 1240 is manually moved to change
the shape of the application by a dental professional until the
desired crown appliance is defined. This process is similar to the
manual sculpting of physical models that is well known in the
profession.
To alter the surface of the electronic model, the dental
professional defines a point on the surface to be moved 1241 and a
region of affected surface 1242 on the electronic model. The region
of affected surface 1242 is a region of area surrounding the point
to be moved 1241. The dental professional then moves the point 1241
to a new location and the processing system alters all of the
points on the surface of the electronic model within the region of
affective surface 1242 to create a continuous surface and smooth
surface between the point being moved 1241 and the remaining
surface of the electronic model 1240.
Specifically, the region of affected surface 1242 comprises a
circle having a fixed radius located about the point being moved
1241. The amount the surface within the region of affected surface
1242 is moved is determined by a blending function that is applied
to points in the region 1242. This blending function may be a
cosine function or an exponential function that is scaled over a
range of 0 to 1 in which the points nearest to the point being
moved 1241 are moved more that the points at the outer radius of
the region 1242. The shape of the blending function may be varied
to control the contour of the surface within the region of affected
area 1242.
As the professional shapes the surface, color mapping of portions
of the electronic model may be used to illustrate the proximity of
the surfaces of the created appliance with adjacent and opposing
teeth surfaces. Additional details regarding the creation and use
of color mapping functions is dental electronic models may be found
in commonly assigned U.S. Provisional Patent Application Ser. No.
60/376,091 titled "METHOD AND APPARATUS FOR ELECTRONICALLY
GENERATING A COLOR DENTAL OCCLUSION MAP WITHIN ELECTRONIC MODEL
IMAGES" filed Apr. 29, 2002, which is U.S. patent application
titled "METHOD AND APPARATUS FOR ELECTRONICALLY GENERATING A COLOR
DENTAL OCCLUSION MAP WITHIN ELECTRONIC MODEL IMAGES", Ser. No.
10/426,252, filed Apr. 29, 2003.
FIG. 13 illustrates a set of processing modules that a CBI
processing system utilizes to implement a method for creating
dental crowns using a lost-wax manufacturing process from
electronic model files corresponding to patient teeth impressions
and corresponding electronic models for tooth crowns. A CBI
processing system is constructed using an eModel manipulation
module 1301, a margin curve processing module 1302, an eModel mesh
specification module 1303, an eModel mesh generation module 1304
and a crown top mesh library 1305. These modules, when used
together, implement the processes described above.
The eModel manipulation module 1301 permits an operator to
manipulate and view various eModel meshes on a computer display
device as needed in the above described processing. This module
1301 includes a move and view module 1311 to place and move eModel
meshes on a display relative to each other. This module 1301 also
includes a scale and size module 1312 to modify the shape of a mesh
during the manipulation process.
The margin curve processing module 1302 performs the processing
associated with the definition and use of a margin curve that is
part of a tooth prep site as needed to define a mesh for the
generation of a dental appliance. The margin curve processing
module 1302 includes a define module 1321, a calc refine margin
point module 1322, and a generate a refined point curve module
1323. The define module 1321 is used by an operator to define the
margin curve about a prep site. The calc refine margin point module
1322 is used to generate the refined margin point using the two
tangent lines to the mesh surface as discussed above. The generate
a refined point curve module 1323 generates a modified mesh surface
that moves the margin curve to the refined margin point for all
points along the margin curve.
The eModel mesh specification module 1303 contains a generate STL
spec file module for processing the internal representation of a
mesh defining a dental appliance to generate an output file
containing a specification for the appliance that may be made using
a rapid prototyping process. As discussed above, the rapid
prototyping generates a wax impression that is usable in a lost-wax
fabrication process to manufacture the dental appliance.
The eModel mesh generation module 1304 and a crown top mesh library
1305 are used to generate the mesh that specifies the dental
appliance. The eModel mesh generation module 1304 includes a top
mesh module 1344, a side mesh module 1342, an offset mesh module
1343, and a combine mesh module 1341. The top mesh module 1344
generates the mesh using pre-defined library meshes that are
obtained from the crown top mesh library 1305. This mesh is
modified in the scale and size module 1312 as needed to fit the
patient's prep site.
The side mesh module 1342 generates the side mesh surface from the
crown top to the refined margin curve defined in the generate a
refined point curve module 1323. The offset mesh module 1343
generates the offset mesh surface that follows the prep site and
provides the offset space needed to install the appliance to the
prep site. The combine mesh module 1344 stitches the three meshes
together into a solid object that is used to generate a
specification for the dental appliance in the eModel mesh
specification module 1303.
FIG. 14 illustrates an operational flow for a method for creating
dental crowns using a lost-wax manufacturing process from
electronic model files corresponding to patient teeth impressions
and corresponding electronic models for tooth crowns. The
processing begins 1401 and proceeds to a define margin curve module
1411. The define margin curve module generates a definition for the
margin curve around the prep site on an electronic model for the
patient's teeth. As discussed above, this curve is used to define
the dental appliance's interface to the supporting tooth
structure.
The processing then continues with an operator defining the crown
top scaling match points in module 1412. As discussed above in
reference to FIG. 8, these match points are used to scale a
normalized crown top library mesh specification to the size needed
for a given patient. The crown top library mesh specification to be
used for the dental appliance is selected from the library in
module 1413 and then scaled to its proper size in module 1414 using
the match points entered in module 1412.
Once the crown is completed, the mesh for the crown top is places
upon the prep site in module 1415. The operator manipulates the
position and orientation of the crown top mesh as needed to place
it into a desired position. This module 1415 also permits an
operator to verify the interaction of the crown top mesh with
opposing teeth to obtain an optimal placement and orientation.
The margin curve is processed in module 1516 to generate the
refined margin curve as discussed above. This refined margin curve
provides a more accurate definition for the bottom of the appliance
while permitting the proper generation of the offset space between
the prep site and the offset mesh. The processing then continues to
module 1417 where undercuts in the offset prep site surface are
removed relative to the insertion vector expected to be used when
the dental appliance is installed onto the prep site.
Once the prep site mesh is corrected, the offset mesh is generated
in module 1418. The offset mesh provides a mating surface to the
prep site surface with allowance for offset space. This offset
space may be a uniform distance of a predetermined value or may be
a varying distance depending upon the location within the prep
site. In a preferred embodiment, the offset spacing is shown to a
dental professional using a color mapping mechanism that
illustrates a distance between the inner and outer surfaces using a
set of colors. A range of similar distances is illustrated by
indicating the distances by superimposing a color from a color map
onto the surface of the CBI appliance. A detailed description of
the color map process may be found in commonly assigned U.S.
Provisional Patent Application titled "METHOD AND APPARATUS FOR
ELECTRONICALLY GENERATING A COLOR DENTAL OCCLUSION MAP", Ser. No.
60/376,091, filed Apr. 29, 2002, now U.S. patent application titled
"METHOD AND APPARATUS FOR ELECTRONICALLY GENERATING A COLOR DENTAL
OCCLUSION MAP", Ser. No. 10/426,252, filed Apr. 29, 2003. These
applications are hereby incorporated herein by reference.
Next, the side mesh surfaces are generated between the bottom of
the crown top mesh and the refined margin curve in module 1419.
This process attempts to define a smooth curved surface. The three
meshes, the crown top mesh, the side mesh and the offset mesh are
merged together in module 1420 to create a specification for a
solid object representing the dental appliance.
Module 1421 is used to permit an operator to adjust the shape of
the dental appliance as discussed above with reference to FIG. 12.
Similar modifications, if desired may be made to the crown top mesh
to correct the interaction of the crown top surface with the
opposing tooth. Once the mesh specification for the dental
appliance is complete, module 1422 generates an output file
containing the dental appliance specification in an STL format.
This file is output and the processing ends 1402.
While the above embodiments of the present invention describe a
system and method for constructing dental crowns, bridges and
implants using a lost-wax process, one skilled in the art will
recognize that other methods of manufacture of the dental devices
are possible. The present invention allows fabrication of fixed and
removable prosthodontic prosthesis such as copings, crowns, inlays,
onlays, veneers, bridges, frameworks, implants, abutments, surgical
stents, full or partial dentures and other hybrid fixed prosthesis
for dental applications. One skilled in the art will easily
recognize that other CBI and orthodontic appliances may readily be
constructed in accordance of the present invention. As such, long
as the manufacturing process utilizes electronic models for
impressions of patient's teeth and corresponding electronic models
for the crown devices, the present invention to would be useable in
other manufacturing methodologies. It is to be understood that
other embodiments may be utilized and operational changes may be
made without departing from the scope of the present invention.
The foregoing description of the exemplary embodiments of the
invention has been presented for the purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise forms disclosed. Many modifications and
variations are possible in light of the above teaching. It is
intended that the scope of the invention be limited not with this
detailed description, but rather by the claims appended hereto.
Thus the present invention is presently embodied as a method,
apparatus, computer storage medium or propagated signal containing
a computer program for providing a method, apparatus, and article
of manufacture for constructing dental crowns, bridges and
implants.
* * * * *